1. Field of the Invention
The present invention is an oilfield treatment vessel for removing water from oil that functions to replace three separate vessels: a gas separator, a free water knockout vessel and a heater treater. The present vessel functions more efficiently than the three vessels it replaces and pays for itself rapidly by reducing installation costs.
2. Description of the Related Art
For the first time ever the present invention has combined the best features of a gas-liquids separator, a free water knockout (FWKO) vessel, and an oilfield heater treater. In most oilfield production operations the use of three individual gas-liquids separators has been considered normal and standard. These individual vessels remove the gas associated with the liquids production, remove easily separated water in a “free water knockout” (aka FWKO), and remove water and emulsion for crude oil in an individual heater treater that heats the liquids to lower viscosity of the oil phase thereby increasing water and emulsion separation rates. This has been the norm for nearly 100 years!
Most oilfield processing has always been accomplished in vertical vessels. In the middle of the last century oilfield process equipment designers discovered that horizontal vessels are at least three times more efficient separators than vertical vessels. Only the paradigm of “we always did it that way” kept the use of vertical vessels like gas separators and vertical heater treaters alive. However, the new millennium is overcoming many of the paradigms of the past, particularly now as the industry strives for higher efficiency and lower costs. The paradigm of individual vessels is costly. It is costly to use three vessels with three sets of controls, three sets of relief valves, three sets of sight glasses, and three sets of fluid control valves. When you add to this three installation costs, and the concept of combining all three vessels into a single horizontal vessel begins to make economic sense. Add to this 21st century vessel internals, and the “three times advantage” increases to five times, or more. Eventually, the use of single vessels may make the use of three separate vessels obsolete.
So, the present invention is a three-in-one vessel. Since it is a three phase separator with an emphasis on removing gas from liquids, free water from oil, and a crude oil heated dehydrator, it can be considered a separator, a FWKO, and a heater treater all combined into one vessel. The present invention will separate up to 6MMSCFD from incoming liquids, and is assisted by its unique hydrocyclone centrifugal inlet diverter and the serpentine vane demisting system, considered to be the ultimate of demisting and coalescing systems. These parallel angular plate vane systems are the most efficient and forgiving demisters known to exist today. They are also self-cleaning. Demisting is important because removing oil mist from gas prevents oil carryover and loss of revenue. Most separators use lesser efficient demisters, and therefore carry over between 0.1 and 1.0 barrel of crude oil each and every day resulting in a loss to the producer of between $2,200 and $22,000 each year. Over the 20 expected life of the typical separator this adds us to between $43,800 and $438,000. Thus, carryover losses almost always exceed the cost of the vessel. So, preventing carryover increases revenue and reduces the loss of valuable hydrocarbons. The present invention prevents these losses through the use of its unique centrifugal inlet momentum absorber and its full diameter serpentine vane demister.
And, since the invention is preventing oil carryover in the outlet gas stream with the use of its serpentine vanes, by extending these vanes below the gas phase and through the oil layer the vanes remove all of the free water in the oil and most of the water of emulsion in the oil. Adding a few more inches of depth in these serpentine vanes adds very little cost, but results in a huge economic benefit for the present invention in its oil treating capacity and effluent oil quality. This results is more oil throughput and lower BS&W in the sales oil, making the present invention more efficient than any other previous oil treatment vessel.
History shows that most significant and predictable problems with standard heater treaters are 1) firetube failures and 2) firetube gasket leaks. The present invention solves both of these problems.
Most firetubes are made from steel pipe. They tend to fail because the firetube is placed in water and the water corrodes the tube or its mineral salts precipitate on the hot surface of the pipe creating hot spots which overheat and cause the pipe to fail. The firetube of the present invention is located exclusively in oil. Since there it is little or no water in contact with the firetube, there is little or no corrosion to the firetube and thus firetubes last indefinitely without failures.
Conventional firetube gaskets fail because firetube flanges and flange gaskets are shop fabricated and ovular in shape rather than being round ANSI standards. The present invention uses no oval firetube flanges or home-made firetube flange gaskets. Instead, the present invention uses only full diameter 48″ ANSI 150 raised face flanges with an ANSI 150 spiral wound gasket. This solves the problem of firetube gasket leaks.
In addition to solving the firetube gasket leak problem, the 48″ flange set gives the owner full open 100% access to the entirety of the present vessel instead of the normal 16″ or 24″ round manways which make ingress and egress far more difficult and dangerous when servicing the interior of the vessel.
The ultimate goal in all oilfield operations is to get the maximum volume of the highest quality produced crude oil to market at the lowest cost and in the fastest time frame. The present invention does this more efficiently than any group of conventional units. This all starts with the initial removal of produced gas to enhance liquid-liquid separation, the separation of all freely separable water from oil and all inlet oil being uniformly distributed directly under the firetube of the present invention to incur maximum heating efficiency to enhance viscosity reduction and oil quality. The oil does not pass through the water layer in the heated section of the present invention as it does in most conventional heater treaters. This benefit insures that no additional water is picked up by the flowing oil. Instead, the inlet oil is distributed into the oil layer where it is heated and where it dehydrates most rapidly.
As the heat lowers the viscosity of the crude, the heavier water falls out. The more the heat the lower the viscosity, and the faster the water separation. This is where most heater treaters stop, but not in the present invention. The present invention routes all oil through a second serpentine vane section to make sure the basic sediment and water (BS&W) concentration in the outlet oil is as low as possible. In most cases the BS&W content of the outlet oil is below 0.1%. The difference between 0.5% and 0.1% BS&W in 400 BOPD is worth just over $35,000 each year to the owner in price penalty deductions. And, with excess BS&W penalties in the $3-$15/barrel range, selling 400 BOPD of off-spec oil now with a $3 penalty in selling price, the present invention will save the typical owner over $438,000 each year. This type of savings will pay for the present invention many times over the life of its use.
In conclusion, the present invention functions as three vessels in one. It has more process capacity and produces higher quality oil and gas than three conventional vessels. The owner pays only for only one installation with the present invention instead of three as would be the case with three conventional vessels. And, the present invention processes more oil, gas, and water in a smaller, more efficient vessel that maximizes cash flow and pays for itself quickly.